/**
 * @program: javase
 * @description:
 * @author: lld
 * @create: 2021-04-11 20:07
 **/
public class FindNum {
    public static void main(String[] args) {
        int[] arr={1,2,3,4,5,7};
        int i=0;
        while (i<arr.length-1){
            if(arr[i]+1!=arr[i+1]){
                System.out.println(arr[i]+1);
                break;
            }
            i++;
        }
    }
}
